Fortunately most ( I think) don't push the limits when spearing, but it would be good to know your buddy has that info in mind if something did go wrong.
I believe it happens more than you might think. During our lobster mini-season here in SE Florida last year a freediver drowned in 40ft of water. Thats not really that deep, and yet when you over exert yourself wrestling on the bottom with bugs, or you're at the end of your breath hold and as you begin to ascend a nice fish comes into range and you decide to go back down for a shot. What happens next is someone finds their dive buddy floating on the bottom, but it's too late.
A lot people aren't weighted properly and are too negative. There's nothing wrong with being a little negative if you're a responsible diver, I do it for shallow water under 30ft. But people need to know their limits and have proper surface recovery time to match their dives. I personally go 3:1 recovery:dive ratio to be safe because it's easy to get separated from your dive buddy so really you are on your own in the aqua jungle.
Since spearfishing and freediving are becoming more popular world wide it would be cool to see more seminars or workshops where these professionals educate the public. And promoting safety should be free because it can save lives. Unfortunately, everything in the states is about $$$ so people will try to turn anything into a "service" and charge you $300-$600 for a freediving safety class... Unreal :crazy:
You can become scuba certified for around $160 on groupon, and in my opinion dealing with compressed air is far more technical since you wouldn't want to get an air bubble in your spine and become paralyzed for the rest of your life for failing to decompress on your ascent.
Just my .02,
Chase 